Flow control device

ABSTRACT

The invention relates to a device for control of the flow through a production tube placed in an oil well. The device comprising a portion of the production tube provided with through orifices and protection equipment for providing resistance to wear by erosion. The protection equipment comprises several add-on sectors assembled around the portion of the tube. Each add-on sector provided with an associated inner stiffener penetrating into the portion of the production tube through at least one through orifice. At least one of the add-on sectors provided with at least one opening extending through the sector and its associated inner stiffener.

TECHNICAL FIELD

The invention is related to a device designed to permit the flow of afluid through a production tube in an oil well or the like.

Such devices may be used in a well to optimize production or injectionof fluids from or into the well as a function of time. It isparticularly applicable to wells in which the fluid enters the well at anumber of different locations along its length.

Various implementations of flow control devices or valves have alreadybeen proposed in the domain of oil wells or the like.

STATE OF THE PRIOR ART

One such device is described in document FR-A-2 790 509, comprises holesformed in a production tube, and a closure sleeve installed on theoutside of the production tube and free to slide in front of each holeformed so as to control the flow therethrough. In this manner, the fluidflow passing through the production tube is adjusted by controlling theclosure sleeve which allows only a limited amount of fluid to passtherethrough either from the underground formation to the surface, orvice versa, depending on the exact function of the well.

However, one major problem with this type of flow control device is thatof erosion of the tube around the holes due to the presence of solids(sand) in the produced fluids, to the extent that the valve can lose theability to control flow effectively and ultimately to fail completely.

Although the entire production tube may be degraded due to wear causedby passage of the fluid, certain localized parts are subject to moresevere wear and deterioration. In particular, this is the case at thecontours around holes through which fluid passes, which are subject towear and damage causing a malfunction of the flow control device. Wearof these contours by erosion may be harmful for the precision of thecontrol device, since these imprecisions can make it possible for flowvariations to arise independently of variations caused by control of therelative position of the closing sleeve and the passage holes.

In order to overcome this problem, it has been proposed to create aprotective envelope extending all around the outer surface of theportion of the production tube comprising holes for passage of fluid, inorder to increase the life of this portion of the tube and at the sametime to reduce the inaccuracies caused by wear due to erosion.

Although the technological solution proposed and mentioned above has ledto relative improvements to the life of the portion of the productiontube provided with the protective envelope, it was quickly realized thatthis technique provided insufficient protection for a device withsuitable resistance to wear by erosion. The simple fact of providing aprotective envelope around the outer surface of the portion of theproduction tube does not provide any protection against wear by erosionof the inner surface of the fluid passage holes. Experiments carried outhave shown that this weakness can also cause equipment deterioration dueto erosion, and thus encourage the appearance of inaccuracies in thefluid flow control.

Thus, to overcome this disadvantage, an insert solution was presentedconsisting of inserting a ring with high resistance to wear by erosion,inside each of the cylindrical passage holes. In this solution, the ringonly extends partially into the passage hole, but it preferably extendssufficiently to protect the entire inner surface of the hole. Inparticular, this technique is described in document FR-A-2 790 509, inwhich the device comprises ceramic rings at the entry to each passagehole in order to reduce wear by erosion caused by circulation of thefluid not only around the contours of the passage holes, but also aroundpart of the inner surface of these passage holes.

The protective ceramic rings on the inside of the cylindrical shapedpassage holes can easily be inserted due to the geometry of thedifferent elements used. Nevertheless, force fitting of this assembly isnot easy for all types of protection inserts, and particularly forinserts with a complex geometrical shape. The shape of passage holes ofdevices for control of the flow through a production tube placed at thebottom of an oil well is very variable, and is in no way limited to asimple cylindrical shape. Consequently, when the shapes of passage holesare complex, techniques known in prior art do not propose any highperformance means of protecting the inside of fluid passage holesagainst wear by erosion.

SUMMARY OF THE INVENTION

The present invention provides a device for control of the flow througha production tube placed in an oil well, at least partially overcomingthe disadvantages with embodiments according to prior art mentionedabove.

More precisely, the invention provides a flow control device in whichthe portion of the production tube is provided with means of protectionagainst wear by erosion acting not only around the contours of theopenings but also at the inner surface of the openings, the protectionmeans easily being adapted to the portion of the tube regardless of therequired geometric shape of these openings.

A device according to the invention comprises a portion of theproduction tube provided with through orifices and means of providingthe device with resistance to wear by erosion, the device alsocomprising a sliding sleeve that can be controlled to adjust the flow.According to the invention, the protection means comprise several add-onsectors assembled around the portion of the tube, each add-on sectorbeing provided with an associated inner stiffener penetrating into theportion of the production tube through at least one through orifice, atleast one of the add-on sectors being provided with at least one openingextending through the sector and its associated inner stiffener.

Advantageously, the control device according to the invention isprovided with very high performance means of protection against wear byerosion, to the extent that the contours of the openings through whichthe fluid circulates are composed of protective add-on sectors, and alsodue to the presence of inner stiffeners matching the inner surface ofthrough orifices formed on the portion of the production tube,consequently preventing contact between the fluid and these throughorifices.

The ease of assembly of the protection means on the portion of the tubecan be entirely independent of the geometric shape of the openings,unlike embodiments according to prior art. The inner stiffeners housedon the inside of the through orifices can be fixed to the add-onsectors, themselves assembled around the portion of the production tube.In this way, the technological solution adopted would not require anyforce fitting of the inner stiffeners into the through orifices, sincethese stiffeners are held in place by the attachment of the sectors ontothe outer surface of the portion of the tube.

The openings through which the fluid passes can then be formed throughadd-on protection sectors and their associated inner stiffeners, and nolonger in the portion of the production tube. This specificcharacteristic provides the possibility of choosing a very wide varietyof opening shapes, without any constraints with regard to the fixationof the anti-erosion protection on the portion of the production tube.

Another advantage of the device according to the invention relates tothe possibility of simply and quickly modifying the shape of openings,by replacing the add-on sectors by other sectors with different openingshapes, without making any modification to the through orifices in theportion of the production tube formed initially.

The protection against wear by erosion achieved by using protectionmeans can be just as efficient when the fluid flows from the surfacetowards the bottom of the well as when the fluid flows from the bottomof the well to the surface.

Preferably, the add-on sectors form a protective envelope around theouter surface of the portion of the production tube to prevent anycontact between the portion of the production tube and the fluid causingwear by erosion, to further increase protection of the outer surface ofthe portion of the tube and more particularly the contours of theopenings.

Furthermore, the use of two clamping rings around the portion of theproduction tube to fix the add-on sectors onto the portion of theproduction tube can facilitate assembly and disassembly of such adevice. In order to cooperate with these clamping rings, each add-onsector may comprise an upper groove and a lower groove located at itsupper end and its lower end respectively. In this case, the upper grooveand lower groove are then capable of being fitted with an upper clampingring and a lower clamping ring respectively.

Preferably, the sliding sleeve is capable of sliding on the add-onsectors in order to close off several openings that may be of differentshapes, in the required manner.

Each add-on sector and its associated inner stiffener can be superposedand each can have approximately the shape of an annular portion,particularly to facilitate cooperation of the add-on sectors with thesliding closing sleeve. Furthermore, the shape of the inner stiffener ofeach add-on sector matches the shape of the through orifice in which itis located, so as to obtain a continuous internal surface of the portionof the production tube.

According to a preferred embodiment of this invention, the innerstiffener of each add-on sector is provided with a seal that fits on theinternal wall of the through orifice in which it is located. In thismanner, fluid cannot pass between the through orifices and the innerstiffeners, which has the effect of significantly increasing theprecision of the flow control, and eliminating any pressure loss betweenthese different elements. Furthermore, the seals provided enable theadd-on sectors to be firmly fixed in the through orifices, considerablyreducing vibrations of these sectors, and shocks between the sectors andthe inner surface of the through orifices.

Preferably, each add-on sector is made from tungsten or a ceramic.

It is possible that the device will include several sets of sectors eachwith different openings.

Other advantages and characteristics of the invention will become clearin the non-limitative description given below.

BRIEF DESCRIPTION OF THE DRAWINGS

This description will be made with reference to the attached drawingsamong which:

FIG. 1 shows a diagrammatic sectional view of an oil well inside which aproduction tube is placed, fitted with its flow control device accordingto a preferred embodiment of the invention;

FIG. 2 shows an enlarged perspective, partially exploded view of a partof the flow control device shown in FIG. 1;

FIGS. 3 a and 3 b show perspective views taken from different angles ofan add-on sector fitted with its associated inner stiffener, used in theflow control device shown in FIG. 2; and

FIGS. 4 a and 4 b show perspective views taken from different angles, ofan add-on sector provided with its associated inner stiffener, accordingto another preferred embodiment.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIG. 1 shows an oil well in production, in which only a lower region isshown. This bottom region may be oriented vertically, as shown,horizontally inclined. If the flow control device is placed in ahorizontal or inclined region of the well, expressions such as“downwards” and “upwards” used in the following description should betaken to mean “in the direction away from the surface” and “in thedirection towards the surface” respectively.

The walls of the well 1 are reinforced by a casing 2. In the region ofthe well shown in FIG. 1, the casing 2 is provided with perforations 4to provide a communication path between the inside of the well 1 and theunderground formation having fluids therein (not shown).

To enable the fluid to be transferred to the surface, a production tube6 is inserted coaxially over the full height of the well 1. Theprotection tube 6 is composed of a number of tube segments connected endto end. Part of the flow control device 10 is made on a portion 8 of oneof these production tube segments 6. Furthermore, in the rest of thisdescription, the segment on which the flow control device 10 is locatedwill in general be called the “production tube 6”.

The production tube 6 defines a duct 12 on the inside, through which thefluid rises to the surface. The annular space 14 delimited between thecasing 2 and the production tube 6 is closed, on each side of the flowcontrol device 10, by annular sealing systems (packers, not shown).Thus, the only way in which the fluid from the natural deposit thatpasses through the perforations 14 into the well 1 can rise to thesurface through the central duct 12 is to pass through the flow controldevice 10.

The device 10 comprises at least one opening 16 at the portion 8 of theproduction tube 6 (several of these openings are shown diagrammaticallyin FIG. 1), these openings 16 opening up on the inside of the portion 8of the tube 6 in the duct 12, and also in well 1 at the annular space14. The openings 16 are preferably inclined such that part of an opening16 opening into channel 12 is higher than the part opening up into theannular space 14 in the same opening. The flow control device 10 alsocomprises a sliding closing sleeve 18, and control means 20 for thissleeve 18 connected to it through a rod 21. In practice, the flowcontrol device 10 is provided with an arbitrary number of openings 16,uniformly or non-uniformly distributed around the portion 8 of theproduction tube 6.

The closing sliding sleeve 18 is installed on the production tube 6, soas to be able to move along a direction parallel to the axis of theproduction tube 6 shown by the arrow F. In this way, the closing sleeve18 can occupy a low or front position shown in FIG. 1, corresponding toa position in which the flow control device 10 is closed. In the sameway, the closing sleeve 18 may occupy a high or back position (notshown) corresponding to a position in which the device 10 is fully open,enabling maximum flow of fluid. Obviously, between these two extremepositions, the protective sleeve 18 may be moved continuously to varythe passage cross-section of the control device 10 at will, andconsequently the flow of petroleum fluid passing through the portion 8of the production tube 6.

As can be seen in FIG. 1, that the production sleeve 18 is installedoutside the production tube 6. Due to the outside position of the sleeve18, the production tube 6 is fitted with dynamic seals 22, 24 fitted inannular grooves formed on the outer surface of tube 6, the seals 22, 24being located above and below the portion 8 of the production tube 6respectively, so as to cooperate with the inner surface of the closingsleeve 18 while forming a sealed joint. The flow control device 10comprises a protective sleeve 26 below the closing sleeve 18 andcolinear with it. The main function of this protective sleeve 26 is tocontinuously overlap the seal 24 when the closing sleeve 18 movesupwards, in other words when the control means 20 are activated in thedirection to open the device 10. Nevertheless, the flow control device10 is designed such that when the protective sleeve is in the highposition, it covers the seal 24 without closing the openings 16 of thedevice 10. This control device 10 is provided with return means designedand arranged so as to automatically bring the protective sleeve 26 intoa position at which it overlaps the seal 24 when the seal 24 does notcooperate with the closing sleeve 18.

The design of the closing sleeve 18, and the design of the various meansthat have been described above and that enable its operation, can beadapted as a function of conditions encountered. The different elementsdescribed are simply presented as examples of particular embodiments.

According to the invention and with reference to FIG. 2, the flowcontrol device 10 comprises the portion 8 of the production tube 6 inwhich several through orifices 30 are formed. In the preferredembodiment described, the device 10 is provided with four throughorifices 30 uniformly distributed around the portion 8 of the tube 6.The flow control device 10 also comprises protection means 32, 34 eachwith resistance to wear by erosion. The protection means 32, 34 includeseveral add-on sectors 32 assembled around the portion 8 of the tube 6,preferably forming a protective envelope around the outer surface ofthis portion 8. The protection means 32, 34 are also provided with innerstiffeners 34 associated with add-on sectors 32, each of the stiffeners34 being fixed to an add-on sector 32. When the add-on sectors 32 are inplace around the portion 8 of the tube 6, each associated innerstiffener 34 penetrates into the portion 8 through at least one throughorifice 30, and preferably through only one of these orifices 30. Atleast one of the add-on sectors 32 should comprise at least one opening16, this opening 16 extending through the sector 32 concerned and itsassociated inner stiffener 34. Preferably, each sector 32 assembled onthe portion 8 of the tube 6 is provided with the same opening 16, or thesame openings network 16. As a result, fluid between the production tube6 and the oil well 1 passes through the openings 16 provided directly onthe protection means 32, 34.

Protection means 32, 34 on portion 8 of the tube 6 are assembled usingthe upper clamping ring 36, and the lower clamping ring 38 placed aroundportion 8 respectively, each of them cooperating with the add-on sectors32. Each add-on sector 32 is preferably provided with an upper groove 40in which the upper clamping ring 36 can be housed, together with a lowergroove 42 in which the lower clamping ring 38 may be housed. To obtain agood quality assembly, the upper groove 40 and the lower groove 42 arelocated at the upper and lower ends respectively of the add-on sectors32. (Note that the “upper and lower ends of the add-on sectors 32”refers to the end of each add-on sector 32 closest to the top andclosest to the bottom of the well 1 respectively, when these sectors 32are assembled on the portion 8 of the production tube 6.) Consequently,the selected assembly technique enables a large diversity in the choiceof the geometric shape of the openings 16, to the extent that theassociated inner stiffeners 34 in which these openings 16 are formedmust not necessarily be force fitted into the orifices 30. Theassociated inner stiffeners 34 are held in place on the portion 8 bymeans of the attachment of the add-on sectors 32 around this portion 8,without it being necessary to use rigid links between these stiffeners34 and the through orifices 30. Furthermore, as an example, theassociated inner stiffeners 34 will preferably be free to slide in theorifices 30 easily as they are put into place. With this arrangement, itis then possible to require that each add-on sector 32 should compriseseveral openings 16 with different shapes such as cylindrical or anapproximately parallelepiped shape. Thus, regardless of the shape ofthese openings 16, there is the same ease of fixing protection means 32,34 on portion 8 of tube 6, this facility being obtained by means ofclamping rings 36, 38.

For example, FIGS. 3 a and 3 b show an add-on sector 32 provided withits associated inner stiffener 34. Several openings 16 are provided,including one relatively large opening with an approximatelyparallelepiped shape, and other smaller openings with a cylindricalshape, used particularly to achieve precise control of low flows.

Also as an example, FIGS. 4 a and 4 b illustrate another type of add-onsector 32 with its associated inner stiffener 34, for which the externalgeometry is exactly the same as the external geometry of the sector 32and the stiffener 34 in FIGS. 3 a and 3 b. However, only one opening 16is formed in this sector 32, this single opening having an approximatelyparallelepiped shape and gradually getting smaller at one of its ends,always in order to obtain good precision for the control of small flows.The fact that the external geometry of the sectors 32 and the stiffeners34 is identical means firstly that these elements can be fixed on theportion 8 identically regardless of the shape of the openings 16 formed,and also that it is possible to change the add-on sectors 32 withoutmaking any changes at the through orifices 30 of the portion 8 of thetube 6.

Thus, the flow control device 10 may include several sets of add-onsectors 32, each set having different shape openings corresponding to agiven flow variation mode. Consequently, depending on the needsencountered, operators can choose the most appropriate set of sectors 32for the required flow variation through the production tube 6, withoutworrying about the ease of attachment of the protection means 32, 34that is always identical. Preferably, the add-on sectors 32 in each setof add-on sectors 32 all have the same opening(s) 16.

As can be seen in FIGS. 3 a, 3 b, 4 a, 4 b, an add-on sector 32 and itsassociated inner stiffener 34 are superposed and are approximately inthe shape of an annular portion. In this way, the outer cylindricalsurface of the add-on sectors 32 is quite suitable to enable sliding ofthe closing sliding sleeve 18, itself preferably being provided with acylindrical inner surface complementary to the cylindrical outer surfaceof the sectors 32. Furthermore, the shape of the inner stiffener 34 ofeach add-on sector 32 is approximately complementary to the shape of thethrough orifice 30 in which it is located. This specific characteristicmeans that the portion 8 of the production tube 6 can have a continuousinternal surface, thus avoiding the need to create pressure losses inthe duct 12 in the production tube 6. The fact that the inner stiffener34 extends over the entire length of the through orifice 30 results inexcellent protection against wear by erosion when the production tube 6is designed to operate such that the fluid passes through it from top tobottom, and therefore from the ground surface towards the bottom of thewell 1.

Apart from the matching shapes as mentioned above, in one preferredembodiment of the invention, the inner stiffener 34 of each add-onsector 32 is provided with a seal (not shown) designed to come intocontact with the internal wall of the through orifice 30 in which it islocated.

The protection means 32, 34, consisting of the add-on sectors 32 andtheir associated inner stiffeners 34, are preferably made from amaterial such as tungsten or ceramic, or any other hard material withhigh resistance to wear by erosion. It is then possible to make anadd-on sector 32 and its associated inner stiffener 34 in a singlepiece, and machining operations are carried out on this piece to makethe openings 16.

Obviously, those skilled in the art could make various modifications tothe flow control device 10 that has just been described as anon-restrictive example only.

1. A device for control of the flow through a production tube placed in an oil well, the device comprising a portion of the production tube provided with through orifices and a protection system comprising several add-on sectors assembled in a clamped arrangement to form a protective envelope surrounding the tube, each add-on sector being provided with an associated inner stiffener penetrating into the portion of the production tube through at least one through orifice, at least one of the add-on sectors being provided with at least one opening extending through the sector and its associated inner stiffener; said protection system providing the device with resistance to wear by erosion, the device also comprising a sliding sleeve that can be controlled to adjust the flow.
 2. The device of claim 1, wherein the protective envelope surrounding the tube is around an external surface of the said portion of the production tube.
 3. The device of claim 1, wherein the add-on sectors are fixed onto the said portion of the production tube by two clamping rings provided around the said portion of the production tube.
 4. The device of claim 1, wherein each add-on sector comprises an upper groove and a lower groove located at its upper end and its lower end respectively, the upper groove and the lower groove being designed to hold an upper clamping ring and a lower clamping ring, respectively.
 5. The device of claim 1, wherein the sliding sleeve is capable of sliding on the add-on sectors in order to close the openings in a known manner.
 6. The device of claim 1, wherein each add-on sector comprises several openings with different shapes.
 7. The device of claim 1, wherein each add-on sector and its associated inner stiffener are superposed and each is approximately in a shape of an annular portion.
 8. The device of claim 1, wherein a shape of the inner stiffener of each add-on sector is approximately complementary to a shape of the through orifice in which the inner stiffener is located.
 9. The device of claim 1, wherein each add-on sector is made from a material selected from group consisting of tungsten and ceramic.
 10. The device of claim 1, wherein the device comprises several sets of sectors, each set having different openings.
 11. A device for control of the flow through a production tube placed in an oil well, the device comprising a portion of the production tube provided with through orifices and a protection system comprising several add-on sectors assembled around the portion of the tube, each add-on sector being provided with an associated inner stiffener penetrating into the portion of the production tube through at least one through orifice, at least one of the add-on sectors being provided with at least one opening extending through the sector and the associated inner stiffener; said protection system providing the device with resistance to wear by erosion, the device also comprising a sliding sleeve that can be controlled to adjust the flow; and said protection system having a clamping arrangement for clamping said add-on sectors to the tube independent of a geometric shape of the through orifices of the tube.
 12. A device for control of the flow through a production tube placed in an oil well, the device comprising a portion of the production tube provided with through orifices and a protection system comprising several add-on sectors assembled around the portion of the tube such that said sectors form a protective envelope surrounding the portion of the tube, each add-on sector being provided with an associated inner stiffener penetrating into the portion of the production tube through at least one through orifice, at least one of the add-on sectors being provided with at least one opening extending through the sector and the associated inner stiffener; said protection system providing the device with resistance to wear by erosion, the device also comprising a sliding sleeve that can be controlled to adjust the flow and wherein each add-on sector comprises several openings with different shapes.
 13. A device for control of the flow through a production tube placed in an oil well, the device comprising a portion of the production tube provided with through orifices and a protection system comprising several add-on sectors assembled around the portion of the tube such that said sectors form a protective envelope surrounding the portion of the tube, each add-on sector being provided with an associated inner stiffener penetrating into the portion of the production tube through at least one through orifice, at least one of the add-on sectors being provided with at least one opening extending through the sector and the associated inner stiffener; said protection system providing the device with resistance to wear by erosion, the device also comprising a sliding sleeve that can be controlled to adjust the flow and several sets of sectors, each set having different openings. 